One will be confronting the growing North Korean nuclear threat, which has gone from bad to worse in recent years. The other: Preserving last summer’s landmark nuclear deal with Iran. It effectively closed off Tehran’s path to a bomb, but faces an uncertain future.

North Korea will be especially vexing. Experts estimate the country has 13 to 21 nuclear weapons and a growing stockpile of fissile materials to make more. Pyongyang may soon be able to target U.S. military installations in Japan, after the successful test of an intermediate ballistic missile last month.

Unfortunately, America seems to have exhausted its options for dealing with North Korea. Diplomacy hasn’t worked, and neither side seems ready to renew negotiations anytime soon.

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Sanctions haven’t worked either, mainly because China, Pyongyang’s biggest trading partner and the closest thing it has to an ally, refuses to enforce them. Beijing fears North Korean nukes. But it fears even more the possibility of Kim Jong-un’s government collapsing under international pressure.

As a result, North Korea has been able to “have its cake and eat it, too,” says Joel Wit, a senior fellow at the U.S.-Korea Institute and cofounder of 38 North, a website devoted exclusively to analysis of North Korea.

With China’s begrudging acceptance, Pyongyang can continue to expand its nuclear program while avoiding the worst consequences of sanctions.

Iran poses a different kind of problem. Last summer’s accord between Tehran and the group known as P5+1 (China, France, Germany, Russia, the United Kingdom and the United States) has worked exactly as intended, constraining Iran’s nuclear capabilities in exchange for sanctions relief.

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But the deal is starting to fray around the edges. The economic boom Tehran expected to follow implementation hasn’t materialized, and Western firms remain reluctant to invest in the country for fear of running afoul of remaining U.S. sanctions (intended to punish Iran for missile tests and supporting terror groups such as Hezbollah).

Congress is also moving to undermine the agreement. Last week, the Republican-controlled House voted to block a major sale between Boeing and Iran and is mulling other measures that would prevent the U.S. from meeting its sanctions relief obligations under the accord.

Unless something changes, and Iran’s economy improves, the political leadership in Tehran will have a difficult time defending the deal to an increasingly skeptical public and hardline elements within the Iranian regime, according to Adriane Tabatabai, an expert on the Iranian nuclear program at Georgetown University. Ultimately, Iran may decide to scrap it — if Congress doesn’t try to first.

So what does the future hold? Much depends on who wins the presidential election. Republican Donald Trump has caused much consternation by pledging to withdraw American troops from the Korean Peninsula, encourage South Korea to acquire a nuclear weapon and “tear up” the Iran deal. But he might take a more pragmatic line once sitting in the Oval Office.

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Democrat Hillary Clinton might feel politically safe enough to pursue Iran-style negotiations with North Korea, in the hopes of convincing the country to give up its nuclear weapons and rejoin the global community. That’s especially likely, Wit reckons, if Democrats also control the Senate.

Whether those negotiations would succeed is an open question, since Pyongyang hasn’t been the most reliable negotiating partner in the past. But the move would mark a welcome shift toward diplomacy after years of confrontation and isolation.

A Clinton presidency would also make the Iran deal’s future a little more secure, a relief to many of the experts following the issue, since, as North Korea shows, once the nuclear genie is out of the bottle, it’s difficult to put back.